The science of physical exercise has long agreed that range of motion is a determining factor of the quality of an exercise apparatus. If an apparatus provides a format of complete range of motion wherein the muscle is challenged when it is elongated as well as when it is contracted, that apparatus is a better as well as when it is contracted, that apparatus is a better provider of muscle development than a lesser range of motion apparatus.
Heretofore, abdominal exercise apparatus have provided only partial range of motion for the abdominal muscles. They do not provided for elongation beyond a middle range of the muscles potential motion. At worst they stop elongating the abdominal muscles when the back is flat: as in the sit-up or curl. And at best they provide the small increase in elongation that occurs when the low lumbar spine is arched to a degree of normalcy in ordinary posture. This is also called "normal lumbo-sacral arch" as in U.S. Pat. No. 4,752,067 to Colonello, Jun. 21, 1988. Neither is acceptable because the abdominal muscles can elongate inches farther than these middle ranges. More complete elongation of the abdominal muscles occurs when the lumbar and thoracic spine are super arched, or in other words, are arched beyond the degree of arch that is common to ordinary posture.
The act of super arching the spine is very common in sports. For example, super arching of the spine is a natural part of overhand throwing. Baseball and softball players perform this motion over and over. As they cock the ball above and behind their shoulder, they super arch their spine. Then, as the ball is thrown, they contract their abdominal muscles and pull or "sling the upper torso forward, thereby adding force to the throwing motion.